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However, while sitting with the woman the witness learned there was a third person involved in the collision, a teenage girl still trapped in her car.

"I saw two people climb down to the girl's car. One lady had a first aid kit but then that same lady started walking back up just shaking her head," he said.

"There wasn't much that could be done."

The witness, who regularly uses Armidale Rd, said he rarely saw anyone speeding but the road structure could cause problems for inexperienced drivers or those unfamiliar with the terrain.

"The lanes are often too narrow and there's some pretty rough surface to drive on at times," he said.

"If you drive to conditions at a suitable speed that's fine, but if you're going a bit too quick or you have to suddenly swerve to avoid something, that road becomes quite unforgiving.

"I came across a log truck rollover some time last year along the same road and they'd come around the corner too quick."

It's understood the section of road where the collision occurred was upgraded by Clarence Valley Council more than a year ago, but the man said a small structural defect in the road, specifically around the bend, could still pose problems for drivers.

"When you come around that sweeping bend where the accident happened, the southbound lane slopes from left to right as it should. But just on the outer edge of that southbound lane the road just curves off a whisker and slopes the other way. It pulls you a little bit and if someone overcompensates just as another car is coming, they could easily land in trouble," he said.

"I don't know what happened with this incident on the weekend and don't want to make assumptions, but the marks on the road show a car going too wide - you can see the wheel mark had gone over that edge."

Police are appealing for anyone with information about the incident to phone Crime Stoppers on 1800333000 or Grafton police on 66420222.